1. Field of Application
This invention relates to systems and methods for analyzing motion; and more particularly to a system and method for analyzing the movement of a portion or portions of a body.
2. Description of the Prior Art
Motion analysis, and more particularly analysis of the movement of specific parts of the human body such as arms or legs, is finding increased use and application in athletics and medically related fields. By analyzing the movement of a baseball player's arm it may be possible to suggest improvements in their swing and hopefully their batting average. More importantly, by analyzing the movement of a person's arm, hip, knee, foot, or other body part, it may be possible to suggest therapy or corrective surgery that will permit easier or less painful use of the body part, or prevent joint or bone deterioration or disorders.
However, observation of such motion by using only the human eye and on-the-spot mental analysis, has not proved definite and accurate enough to be effective. The motions are too quick in time and too lost in space to be accurately remembered or recorded. Additionally, it may be quite painful to the subject to keep repeating the motion so that the observer can perceive an accurate mental picture of the motion and make an on-the-spot analysis.
Various methods and systems have been created which utilize equipment to provide a sensible output related to the motion to be analyzed, and a record of the output so provided for use in analyzing the motion. Some of these systems make the record by use of motion photography and thus must wait the developing of the film to even determine if the desired motions were properly recorded for analysis purposes. Other systems require complex computer hardware and software packages and trained technicians thus greatly adding to the cost of the equipment itself and the acquisition and analysis of the data.
Quite often the motion analysis system requires the attachment of the subject by cables to remote sensors such as shown in an article by Strelow et al entitled "Apparatus For Measuring And Recording Path Velocity And Direction Characteristics of Human Locomotion" that appeared in Behavior Research Methods and Instrumentation, Vol. 8, No. 5, pp. 442-446, October 1976; or the placing on the subject of sensing devices that are in turn attached by electric cables to remote recording devices such as described in an article by Smidt et al, entitled "An Automated Accelerometry System For Gait Analysis" that appeared in J. Biomechanics, Vol. 10, No. 5-6, 1977 pp. 367-375, or as shown in U.S. Pat. No. 3,699,856 granted on Oct. 24, 1972 to R. W. Chiabot et al for Movement Monitoring Apparatus. The attachment to the subject of equipment or devices having any weight factor will most probably modify the body motion to be analyzed and add a variable to the analysis and calculations that may be difficult, if not impossible, to factor out. Furthermore the attaching to the subject of cables, electric or otherwise, not only adds an additional weight factor but may also impede and possibly modify the motion under study.
The subject under study may be somewhat less restricted in their movement by devices such as those shown in U.S. Pat. No. 3,717,857 granted to J. W. Evans on Feb. 20, 1973 for Athletic Swing Measurement Systems which utilize a radio transmitter to send the sensed signal to a remote receiver. But they must still carry a motion sensing device and radio transmitting apparatus. The weight and location of such devices may still affect the motion being sensed and add to the analysis variables which cannot be factored out.
The subject can be freed of attached devices and cables by providing a surface and sensors responsive to the subjects motions upon the surface such as the force plate/piezoelectric sensor combination shown in U.S. Pat. No. 3,894,437 granted to J. L. Hogy on July 15, 1975 or Method And Means For Dynamic Gait Analysis, or the mattress and capacitive motion sensor combination shown in U.S. Pat. No. 4,320,766 granted to J. Alihanka, et al on Mar. 23, 1982 for Apparatus in Medicine For The Monitoring And Or Recording of The Body Movements Of a Person On A Bed, For Instance Of A Patient. However, the equipment and method of the later patent is of little utility if the body motion to be monitored requires walking or similar body movement; while force plates are usually of limited size and may not be suitable if the problem under study becomes more pronounced with continued body motion over a period of time.